Tire retreading mold



Filed Aug. 5, 1950 2 SHEETS SHEET 1 19, 1 P. E. HAWKINSON I 2,607,079

TIRE RETREAI-DING MOLD fdZZJan JMzz Aug. '19, 1952 P; E. HAWKINSON 2,607,079

TIRE RETREADING MOLD 2 SHEETS-SHEET 2 Filed Aug. 5, 1950 fatented Aug. 19, 1952 Paul E. Hawkinson, Minneapolis, assignor to Paul E. Hawkinson Company, Minneapolis, Minn, a corporation of Minnesota Application August 5, 1950, Serial No. 117,932

My invention relates to the art of tire retread- 'ing, and, more particularly, to tread curing inatrices of the type disclosed in United States Paten'tjNo. 2,065,697.

Inth'e use of molds of the type immediately above-described, particularly where the tread design-forming ribs are spaced apart circumferentially to provide between th cooperating ribs a relatively wide rubber tread lug, I have found that, frequently, inadequate pressure is obtained between the old and new rubber in the central portion of the lug. This objectionable feature, I have found, may be overcome by utilizing elongated narrow pressur elements in the mold approximately at the point where this lack of pressure occurs. These pressure elements have considerably less radial depth than the design-forming ribs and, therefore, do not, in any way, reduce the effective width of the lugs.

A still further object of my invention is the provision of novel pressure elements which impart a rather decorative appearance to the tread but do not detract from its wearing or traction.

The above and still further objects of my invention will become apparent from the following detailed specification, appended claim, and attached drawings.

Referring to the drawings, wherein like char- :acters indicate like parts throughout the several views:

Fig. 1 is a perspective view of a retreading matrix built in accordance with my novel invent on;

Fig. 2 is a fragmentary view in section of the device shown in Fig. 1;

Fig. 3 is an enlarged view in side elevation of the pressure elements utilized in my novel matrix, some parts being broken away and some parts being shown in section;

Fig. 4 is an enlarged fragmentary section taken on the line 4-4 of Fig. 2; and

Fig. 5 is a fragmentary perspective view of a tire casing with a tread thereon cured in the mold of Fig. 1.

Referring with greater particularity to the drawings, the numeral l indicates, in its entirety, a retreading matrix of the "Hawkinson" type and preferably formed from an endless band of sheet metal. Adjacent its side edges. the mold l is formed to provide circumferentially-extended radially inwardly-projecting tread material co-nfining fianges 2. On the outer peripheral surface 3 of the mold l is spirally wound a tubular coil 4 for conducting steam or other fluid heating medium. The confining flanges 2 define therebe- 1 Claim. (o 18 -18 tween a [cavity 5 in which the tread 6 .of a pneumatic tire I is cured.

Within the cavity 5, a plurality of parallel design-forming ribs'B project angularly, but genjerally laterally inwardly, from the confining flanges'z. As shown, ribs8-have a radial depth only "slightly less than that of the'ribs 2; Furthermore, the ribs 8 as shown particularly in Fig. 2. terminate in the central portion of the matrix I, preferably and as shown, just short of the exact transverse center thereof. Also, as shown, the ribs 8, associated with one of the flanges 2, are staggered with respect to the ribs associated with the opposite flange 2. At their free ends. the ribs 8 are spaced from the ribs 8 on the opposite side of the matrix a distance greater than the width of the ribs 8. In this manner, a continuous though zig-zag riding strip 9 is formed on the tread 6.

The cooperating pairs of parallel ribs 8 are spaced apart circumferentially a distance considerably greater than the width of one of said ribs, whereby to produce therebetween relatively Wide rubber lugs or bars [0. In order to insure adequate pressure being exerted between the uncured rubber and the old casing at the central portion ll of the wide lugs I0, I provide, intermediate each cooperating pair of design-forming ribs 8, elongated and narrow pressure elements l2 which are similar to the ribs 8 in construction but are shorter than said ribs and of considerably less radial depth than said ribs. Both the ribs 8 and the pressur elements [2 may be stamped from sheet metal and secured to the internal peripheral surface l3 of the matrix I by soldering or the like, not shown.

As shown, the pressure elements [2 are centrally positioned intermediate the ribs 8 and extend generally parallel thereto. Furthermore, the pressure elements l2 on one side are in alignment with a design-forming rib 8 on the opposite side of the matrix.

By use of these pressure elements I2, I have found that adequate pressur in all portions of the matrix to insure uniform curing results.

My invention has been completely tested and found to be satisfactory for accomplishment of the above objects; and, while I have shown a commercial embodiment of the invention, it will be obvious that the same is capable of modification without departure from the spirit and scope of the invention, as defined in the claim of the invention.

What I claim is: A tire retreading matrix comprising a cylindrical band, circumferentially extendin parallel tread material confining flanges projecting inwardly from the band adjacent the opposite edges thereof, a series of uniformly spaced circumferentially arranged tread design-formin ribs projecting inwardly from each flange and terminat-.

ing adjacent the circumferential center line of said band, the ribs having a depth slightly less than that of the flanges, the ribs of both series being parallel and disposed at a common angle to the axis of the band and the ribs of each series being disposed in staggered relation to the ribs of the other series, th ribs being circumferentially spaced from each ether at distances substantially greater than the Widths thereof for providing tread lugs of substantial circumferential extent, the free ends of the ribs of the two series thereof being spaced at distances greater than the widths thereof for providing a continuous un broken road engaging surface at the central portion of a tread formed in the matrix, a series of elongated relatively narrow pressure elements disposed intermediate the ribs of each series thereof and having a depth materially less than that of the design forming ribs. and said pressure element of each series being in transverse align- REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,127,517 Richardson Feb. 9, 1915 1,280,382 Braunwarth Oct. 1, 1913 1,917,262 Hawkinson July 11, 1933 2,065,697 Hawkinson Dec. 29, 1936 2,331,680 Hawkinso-n Oct. 12, 1943 2,333,588 Schaevitz Nov.'2,fl1943 2,415,291 Kreyer Feb, 4,1947 2,457,370 Hawkinson Dec. 28, 1948 

